Power shift transmissions having various transmission ratios, in which the shifting between the different transmission ratios occurs as a function of the load or of a required driving speed, are known and have been used for many years particularly in the automobile industry.
Furthermore, it is known to design such transmissions in connection with planetary transmissions and clutches in a modular system, so that the power shift transmissions can be operated by an appropriate design and arrangement of the gear pairings of the planetary transmission in different operation modes, such as a fixed drive mode, a gear reduction mode or a reverse mode. Thus, power shift transmissions are used as a preliminary stage of a transmission in tractors produced by the agricultural machine manufacturer John Deere, which, depending on the design of a stepped planetary set can be operated in the fixed drive mode or reverse mode operation mode, or in the fixed drive mode or gear reduction mode operation mode. The mentioned transmission is characterized in that, in a first shifting operation, a clutch connected to an input shaft connects the input shaft to the output shaft, so that the transmission can be operated in the fixed drive mode, wherein the planetary transmission runs as a free wheel. In a second shifting, the clutch is released, so that the planet carrier is driven by the input shaft, and the planetary set rolls about a first sun gear that is connected to the driveshaft and that is driven by the planetary set. Depending on the arrangement of the planetary set or the design of the gear sets of the planetary set and the sun gears, the power shift transmission can be operated in the gear reduction mode or in the reverse mode.
Thus, a two-stage power shift transmission is provided that on the one hand is produced at high cost in terms of manufacturing technology, and on the other hand does not allow an additional operation mode, for example, a crawler gear mode, in the mentioned arrangement.
The problem underlying the invention is to provide a power shift transmission of the type mentioned in the introduction, by means of which the above-mentioned problems can be overcome.